Accordingly it is already known to cross-strap a pack by first strapping it at a first work station transversely to its direction of conveyance and then, without rotating it, to strap it at a second work station in its direction of conveyance, and next, without strapping it. Such apparatus is shown in the above cited German patent document DE 41 00 276 C2.
Longitudinal strapping—also called inline strapping—is problematical relative to cross-strapping because steps must be taken to move the strap guide duct out of the pack's path, i.e. out of the inside contour of this pack. This problem is attacked in the strapping apparatus of DE 41 00 276 C2 by bending and twisting the strap guide duct in a special way as a result of which said duct shall not interfere with the pack when moving through the apparatus. On the other hand such a duct represents manufacturing difficulties because being a spatial structure curving in many directions. Moreover each apparatus size entails a different strap guide duct mold.
Many attempts already have been undertaken and are documented in the state of the art to find other solutions to this problem.
The strapping apparatus disclosed in DE 196 32 728 C2 offers a strapping frame which shall be pivoted as needed about a horizontal axis situated underneath the work surface into the strapping position when the pack to be strapped assumes its position. The consequent mechanical implementation is comparatively costly. Similar considerations apply to the longitudinal strapping apparatus of DE 101 03 409 A1.
DE 42 30 730 A1 shows a strapping apparatus comprising a strap guide duct fitted with a rectilinearly displaceable frame element which together with an affixed frame element constitutes such a twisted segment. In this disclosure again at least some portions of the strap guide duct are twisted.
EP 0 545 105 B1 discloses apparatus longitudinally strapping a pack wherein the strap guide duct comprises two segments running parallel to the plane of strapping and on opposite sides of the strapping plane along the diagonally mutually opposite zones of the pack and at such a distance from the strapping plane that they shall not hamper the pack's motion, said segments being connected to each other by means of other segments crossing the strapping plane. Such a tape duct too is comparatively complex.
Another apparatus, also disclosed in EP 0 545 105 B1, provides that the strap guide duct substantially run in a plane obliquely intersecting the strapping plane in an intersection line perpendicular to the direction of conveyance, and in that the binding head be pivotably supported about an axis situated in said line of intersection and is driven in a way that when the tape is inserted it assumes an angular position wherein its longitudinal center plane coincides with the plane of the strap guide duct, and in that said binding head shall pivot into the strapping plane when the tape is tensioned. Such apparatus is complex and costly in particular as regards its control and furthermore it incurs high mechanical stresses due to the binding head being driven in pivotable manner, and it is susceptible to malfunctions.
EP 1 207 107 A1 discloses a strapping apparatus comprising a strap guide used to form a strap loop in a waiting position regardless of the position of body being strapped, a loop displacing element being used to drive the strap loop formed by the guide from a waiting position in the apparatus' bench plane into a stacking position around a body to be strapped. In other words, a strap loop is prepared in a horizontal position and, following the positioning of the pack to be strapped, it is pivoted upward into a position from which said loop may strap the pack. This design requires driven gripper segments gripping the strap loop and erecting it along curved arms.
The above described apparatus operating on very different principles are comparatively complex/expensive relative to the initially cited German patent document DE 41 00 276 C2, in particular those requiring additional drives for the sealing unit, the strap guide duct or the erection of the loop.
Accordingly it is the objective of the present invention to create, on the basis of DE 41 00 276 C2, apparatus to longitudinally strap packs without requiring special drive mechanism requirements and allowing comparatively simple manufacture of the strap frame.